1. Field of the Invention
The present invention relates to an optical transceiver used in an optical LAN system and transmits/receives optical signals, in particular, the invention relates to an optical transceiver with a pluggable function to a host system.
2. Related Prior Art
An optical pluggable transceiver, which installs a light-emitting device and a light-receiving device and transmits or receives optical signals by mating with an optical connector, includes a body to enclose a plurality of electronic components and a substrate for mounting the electronic components and an optical receptacle to mate with the optical connector. As disclosed in the United States Patent published as US 2004/105633A, the pluggable transceiver is used such that the transceiver is inserted into a cage that is installed on the host system and is engaged in an electronic plug provided in the rear end of the transceiver with an electronic connected installed in a deep end of the cage.
FIG. 4 illustrates a conventional pluggable transceiver 1 and a cage 2 on the host board 4. The optical transceiver 1 provides the optical receptacle 6 and a body 5 with a rectangular cross section and made of metal. Within the optical transceiver 1 is installed with optical devices, such as a light-emitting device and a light-receiving device, some electronic circuits to drive the light-emitting device or to amplify a signal output from the light-receiving device, and a circuit board to mount the electronic circuits. The optical transceiver 1 is inserted into the cage 2 that exposes an opening 3a on a front bezel 3 of the host system and is mounted on the host board 4. The transceiver 1 is inserted into the opening 3a of the cage 2 and the electronic plug provided in the rear end thereof mates with the electronic connected provided in the deep end of the cage to communicate the transceiver 1 with the host system.
The optical receptacle 6 mates with an optical plug 7, which couples an optical fiber in the optical plug 7 with the optical devices in the optical transceiver to carry out the optical communication therebetween. The optical plug 7 may have a type to be latched with the optical receptacle, such as the LC type optical connector. Furthermore, the optical transceiver 1 provides a bail 8 around the optical receptacle 6 to release the optical transceiver 1 from the cage. That is, when the optical receptacle is free from the optical plug 7, the optical transceiver 1 may be disengaged from the cage by rotating the bail in front of the optical receptacle 6.
FIGS. 5A and 5B illustrate the optical transceiver 1 inserted into the cage 2, in particular, FIG. 5A shows that the optical receptacle 6 is free from the optical plug 7, while, FIG. 5B shows when the optical plug 7 is set within the optical receptacle 6. The cage 2 provides a plurality of fingers 2a around the opening 3a, which comes in contact with the edge of the opening 3a in the bezel 3 when the cage, in particular, the opening 3a thereof exposes from the bezel 3 by mounting the cage 2 on the host board 4 to electrically come the cage 2 in contact with the ground of the bezel 3. Although the cage 2 is grounded to host board 4, it is quite preferable to ground an electrical component at a plurality of positions with a shorter wiring length as possible to reduce noises with high frequency components.
That is, to make the cage finger 2a at the peripheral of the opened edge of the cage 2 contact to the bezel 3 may reliably shield a gap between the cage and the opening 3a of the bezel 3, which may prevent the noise generated in the host system and having high frequency components not only leaking from the gap but also invading therefrom.
Moreover, as disclosed in the United States Patent, U.S. Pat. No. 6,335,869, the metal cover 5 of the transceiver 1 provides a plurality of elastic fingers 5a that come in contact with the inner surface of the cage 2 when the transceiver 1 is inserted within the cage 2. Thus, the metal cover 5 may come in electrically contact with the cage 2 by the fingers 5a, which grounds the metal cover 5 and shortens the length from the cover 5 to the bezel 3. The elastic fiber 5a may be called as an EMI (Electro-Magnetic Interference) finger or a ground finger.
As shown in FIGS. 5A and 5B, the elastic finger 5a is generally formed by making a U-shaped slit in the metal cover and tapping out a portion surrounded by the slit, or by welding a tab bent in advance with the metal cover 5. However, depending on the dimensional tolerance of the cover 5 and the cage 2, and the condition to insert the transceiver 1 into the cage 2, the reliability of the contact between the finger 5a and the cage 2 varies, which causes the electrical instability of the transceiver 1.
On the other hand, to strength the elasticity of the finger 5a to secure the contact against the cage 2 will make it difficult to insert the transceiver 1 into the cage 2 or to extract therefrom. Moreover, the finger 5a with a conventional configuration is easy to deform by iterating the insertion or extraction of the transceiver 1. In addition, the cage 2 has a large dimensional tolerance because it is formed by bending a metal plate, which causes the unreliable contact between the cage 2 and the finger 5a. 